Power failure protective system



Dec. 2, 1941. .1, 'r. CARLSON POWER FAILURE PROTECTIVE SYSTEM 2Sheets-Sheet 1 INVENTOR Jblm Z (arisen ATTO NEY Filed April 22,1939

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Dec. 2,1941. J.- -r. CARLSQN POWER FAILURE PROTECTIVE SYSTEM 2'Sheets-Sheet? Filed April 22, 1939 4 lNVENTOR v Jo/m Z. far/son BYa- 5/ATTORNEY Patented n... 2, 1941 John '1. Carlson, Dayton, Ohio, assignmtoThe Master Electric Company, a corporation of Ohio Application April 22,1939, Serial No. 269,549

. 15 Claims.

This invention relates to a power failure protective system, and moreparticularly to a system and device for the protection of electricallycontrolled heat-producing apparatus upon the occurrence of a powerfailure.

An object of this invention is the provision of an'improved safetydamper control system.

Another object of this invention lies in the provision of an improveddevice which will auprovision of a device for automatically closing thedamper of a furnace upon power failure, even though the dampercontrolling system is in its damper opening position.

These and other features, capabilities and advantages of the inventionwill appear from the subjoined detailed description of one embodimentand a modification thereof, illustrated in the accompanying drawings, inwhich:

, Fig. 1 illustrates the circuit connections of my novel power failureprotective system, the power failure switch thereof being drawn to anexaggerated scale;

Fig. 2 is a cross-sectional view along the line II-II of the switchillustrated in Fig. 1;

, Fig.3 is a partial view of the control system illustrated in Fig. 1,showing the power failure switch and damper in another position; and

Fig. 4 is a front view of a portion of the power failure switchillustrated in Fig. 1, showing a modified constructional detail.

Referring generally to the damper control system illustrated in Fig. 1,it will be noted that my power failure protective switching device 2,more particularly described hereinafter, is adapted to be connectedbetween the motor 4 which controls the draft damper 6 of a furnacegenerally indicated at 8. The protective device 2,is adapted to be usedwith the usual damper controlling apparatus which may consist 'of acontrol thermostat lll, usually a room thermostat, a circuit commutatingdevice l8 rotated by the damper motor 4, and the control arm 36interconnected with the damper over suitably positioned means such aspulleys 31 by means of a chain or other connecting device 38.

raised position due to the fact that the control thermostat I is in its"on position. 'At'this time no electrical circuits will be established.If, however, the room thermostat moves to its "off position the dampermotor 4 will be energized to rotate the crank 36 upwardly and thus lowerthe damper; 8 to its closed position. Such a circuit can be traced fromone side of the source of power 40, conductors 42' and 44, damper motor4, conductors '46 and 48, arm 12 and contacts l4 and it of thethermostat l0, conductors 50 and 52, brush 30, contacting plate andbrush 32 of the commutating device l8, and conductors 54 and 56 to theother side of the source of power. The motor thus being energized, willstart to raise the arm 36, thus lowering the damper 8 and at the sametime rotate the commutating device It. After this commutating device hasbeen rotated to a slight degree, control'of the motor 4 is taken awayfrom the room thermostat III to insure closing of thedamper'despite thefact the room thermostat may have movedirom the"off position. A circuitis established from one side of the source of power 40, throughconductors 42 and 44, damper motor 4, conductors 46' and 60, brush 28,conducting plate 20 and brush 32 of the commutating device l8 andconductors 54 and 56 to the other side of the source of power 40. Itwill be noted that shortly after the brush 28 makes contact with theconduct.- ing plate 20, the brush 3!! through which the circuitincluding the room thermostat ID was first established, will meet thecut-out or insulated portion 26 of the commutating device I8, thusbreaking the circuit. The damper motor will, however, continue to rununtil the brush 28 meets the cut-out portion 24 of the commutatingdevice I8. This breaks the circuit to the damper motor, providing theroom thermostat has remained in its off" position,. and the damper 6will remain closed until a contrary call is received from the thermostatHi. If now, the thermostat moves to its "on position a circuit forrotating the damper motor 4 to raise the damper will be established fromone side of the source of power 40, conductors 42 and 44, damper motor4, conductors 46 and 48, arm l2 and contacts I4 and 18 of the thermostatl0, conductor 58, brush 34, contacting plate 20 andbrush 32 of thecommutating device l8, and conductors 54 and 56 to the other side of thesource of power 40. Again, after slight rotation of the commu- Thefurnace damper 6 is illustrated in its 56 tating device ill, a circuitis established for the damper motor, which insures its continuousenergization until the damper 6 is raised, despite a 28, which has nowmoved out of the cut-out section 24, contacting plate 28 and brush .82of the commutating device I8, and conductors 84 and 88 to the other sideof the source of power 48. The damper motor will accordingly run untilthe brush 28 enters into the cut-out portion 22, at which time thedamper will be in its open position. After a short movement of thecommutating device I8, the previously energized brush 84 moves into theslot 28 and thus breaks the circult-to the room thermostat.

It will be noted from the aforedescribed operation of the dampercontrolling system that no mention was made of the power failureprotective switching device 2, which,- however, was at that timeelectrically interconnected with the control circuit through conductors88, 88 and I8 and I2, and mechanically by the fact that the chain orcord 88 interconnecting the rotating arm 88 of the damper motor with thedamper 8, passed over pulleys I8, I8 and 88 of the control mechanism.This accordingly shows that for normal operation the device 2 playsnopart in the damper control-system, but, as hereinafter set forth, isonly effective when necessary upon a power failure.

Before describing the manner in which the device 2 is controllablyconnected to the damper control circuit, a description of this devicewill first be given. As more specifically illustrated in Figs. 1 and 2,upon a suitable plate I4, are rotatably mounted a pair of free pulleysI8 and 88, and a lever arm 82, shown as pivotally connected thereto at84. The plate I4 is also provided with a stop 88 for limiting motion ofthe lever arm 82 in the counter-clockwise direction as seen in Fig. 1. Asuitable spiral spring 88 tends to urge the lever arm 82 against thestop 88. As shown in Fig. 1, the lever arm 82 is also provided with afree pulley I8 and urged in the clockwise direction due to the weight ofthe raised damper 8 transmitted to the pulley I8 by chain 88 passingover the pulleys I8 and 88. Thi motion is restrained, however, by thefact that the point 88 of the lever arm 82 engages the extended part 82of a second lever 84. also pivotally mounted on the plate I4 as at 88,but held against counterclockwise movement by the co-action of apoleface 88 with the energized solenoid 82. It is to be noted at thispoint, that the spring 88 urging the lever arm 82 in thecounter-clockwise direction is not strong enough to overcome theclockwise force exerted by the weight of the damper 8 when in its raisedposition. Accordingly, in the position of the part shown the clockwisemotion of the lever arm 82 is only restrained by the engagement of itspoint 88 with the extension 82 of the second lever 84. It is also to benoted that the strength of the spring I88 is not sufiicient to overcomethe attractive force of the solenoid 82, but is only used to insure apositive movement of the lever 84 upon the de-energization of thesolenoid 82. As illustrated, the solenoid 82 is also mounted upon theplate I4 by any suitable means, such as bracket I82.

Suitably mounted upon the rear of the plate I4 of the device 2, is aswitch 84. The switch 84 is preferably actuated by means of a button I84projecting through the plate andextending outwardly from the frontthereof. The button I84 is mounted upon a contact arm I88which, whenpressed inwardly by pressure upon the button I84 is 'adapted'to contacta second contact arm I 88. The contact arms I88 and I88 may be suitablymounted upon the rear of the plate 14 by means indicated as insulatingmembers H8 and H2 respectively.

As will be noted from a comparison of Figs. 1 and 3, the button I84 ofthe switch 84 lies in the path of rotation of the lever arm'82.Accordinsly. when the lever arm 82 is released upon the de-energizationof the solenoid 82 and rotates in a clockwise direction through theweight of the damper 8 acting upon the pulley I8, the button I84 will bedepressed by the lever arm 82 and thus establish contact between theswitch arms I88 and I88.

Referring now to Fig. 1, it will be noted that the solenoid 82 of theprotective switching device is directly connected to the source of power48 by conductors 42, 88, 88 and 88. Therefore, as long as power is beingsupplied to the damper control circuit, the solenoid 82 will remainenergized and hold the lever arm 84 in a suitable position to restrainmovement of the lever arm 82. Assuming that in response to movement ofthe thermostat I8 to its on position the damper motor 4 has alreadyraised the draft damper 8, the various elements of the damper controlsystem will be in the position illustrated in Fig. 1. If now a powerfailure occurs, and the damper control were directly connected to thedamper 8. these parts would remain in the same position, since due tosuch power failure, the control circuit would not be effective. Thedamper 8 would therefore remain open despite a contrary call of thethermostat I8, and the house or other structure would become overheated,and perhaps overheated to such a degree, as to create the gravepossibility of a fire.

The use of the protective switching device 2, as connected in Fig. 1entirely avoids this dangerous possibility. Upon failure of the power asource. the solenoid 82 will become de-energized. and the spring I88will rotate the lever arm 88 in a counter-clockwise direction to releasethe lever arm 82. The raised damper. 8, however. will, through itsweight, pull the lever arm 82 in a clockwise direction and, at the sametime, close the draft of the furnace.

The relative movement of the pulley I8 on the lever arm 82 and themovement of the draft 8 are so proportioned, as seen for example in Fig.3, that the upper position of the lever arm 82 is such as will permitcomplete closing of the draft 8. It will therefore be seen, that in theevent of a power failure when the furnace drafts are open, these draftswill be immediately closed and all danger of overheating is removed. If,of course, the draft is in its closed position upon the occurrence ofpower failure. no upward force will be exerted on the lever arm 82 andthe spring 88 is sufficient to maintain the lever arm in its downwardposition even though the solenoid 82 becomes de-energized and releasesthe stop 82.

Accordingly, one important feature of this device 1 lies in the factthat it is only effective when necessary, and permits the normaloperationon the damper control at all other times.

Upward movement of the lever arm 82 upon failure of power not only iseflective to close the furnace damper 8, but, by depressing the button I84 of the switch 84, establishes a circuit to restore normal control ofthe damper controlling apparatus upon the recurrence ofthe power. It isalso effective to return the elements of the dethe source of power 48,conductors 42 and 44,

damper motor 4, conductors and I8, switch arms I88 and I88, conductorsI2 and 82, brush 38, conducting plate 28 and brush 82 of the commutatingdevice I8 and conductors 54 and 58 to the other side of the source ofpower 48. The damper motor 4 will accordingly rotateto raise the dampercontrolling arm 36 and thus pr'oduce slack in the chain or cord 88. Thetension on the pulley I8 due to the weight of the damper 6 isaccordingly released and the spring 88 will then be effective to returnthe lever 82 in a counterclockwise direction to its original-position.The stop 82 on the lever arm 84 will not prevent this action since, asis clearly seen in Fig. 3, the poleface 88 on the lever arm 84 has beenmoved away from the solenoid 62 to such an extent that there-energization of the solenoid is ineffective to lock the lever arm inits controlling position until the leverarm 82 has substantially reachedthe end of its counter-clockwise movement. At this point a cam actionbetween the edges of the levers 82 and 84 will take place to move thepole-face 88 of the lever 84 within range of the pulling power ofthesolenoid 82 and the lever 84 will then be moved into its lockingposition as shown in Fig. 1.

If, after the aforedescribed action has taken place after return ofpower, the thermostat I8 is still in its on position, the damper motor 4will continue to rotate to raise the damper 8, although the protectiveswitch device is now in its original position and ready for action incase the source of power again fails. The circuit .for the damper motor4 to raise the damper 8 can be traced from one side of the source ofpower 88, conductors 42 and 84, damper motor 4, conductors 48 and 48,arm I2 and contacts I4 and I8 of the thermostat I8. conductor 58, brush38, conducting plate 28 brush 32 of the commutating device I8, andconductors 54 and 58 to the other side of the source of power 88.

If at the time of restoration of power the thermostat I8 is in its oif"position, the same sequential action as above described will take place,since the contacts of the switch 68 are in shunt to the "ofi contacts l4and I6 of the thermostat.

If a power failure occurs when the room thermostat I8 is in its "offposition, there is no need for the protective device to act and it willnot act because there will be no weight on the chain 88 effective tolift the lever arm 82, since the damper 8 is already in itsclosedposition.

' It will accordingly be seen that one of the great advantages of theproposed protective system and protective device lies in the fact thatit 82'. In this case, the tip of the lever arm 82 is formed'as a pawlI28 pivoted thereto at I22 and pressed by a spring I24 against anabutment I28. when such an arrangement is used, the spring I88 need notbe present to move the pole-face 88 of the lever arm 84 away from thesolenoid 62 to such a degree as illustrated in Fig. 3. Even if upon therestoration of power the lever arm 84 is returned to its lockingposition before the lever arm 82 has descended to its original normalposition the spring pressed pawl I28, being yieldable in thecounter-clockwise direction, permits complete return of the lever arm 82under the action of the spring 88.

While it has not been illustrated, it will be obvious to those skilledin this art that the solenoid 82 might act directly upon the end oflever arm 82, without the use of the intermediate looking arm 84. Inthis case a suitable pole-face would be provided on the lever arm 82.

In accordance with a preferred arrangement,

the protective switching device may be mounted within a box (not shown)near the ceiling ofv the basement, the box protecting the mechanism fromdirt and moisture. The pulleys I6 and 88 are not necessary for propermovement of the lever arm 82 as long as the chain 88 exert a force intheproper direction upon the pulley I8 under action of the weight of thedamper 8. If the pulleys I6 and 88 are used. however, proper movement ofthe lever arm 82 is assured.

The source of power has been generally indicated at 48. This source ofpower is preferably a transformer connected to the usual power lines,although any source of power can be used provided the damper andsolenoid coil are designed therefor.

While it has not been illustrated, it will be obvious to those skilledin this art, that the damper motor 4 maybe positioned with anothercontrolling arm mounted diametrically opposite to the rotating 36, whichcan be used to control the check damper of a furnace. In this case, thecheck damper will be closed when the draft damper is open and viceversa. I

The type of commutating device illustrated as used with the damper motor4, is only diagrammatically portrayed, and it is intended that anysuitable construction for carrying the proper sequential energization ofthe control circuits may be used.

It is to be understood that the damper con- I do not intend to limitmyself theretoexcept as may be required by the following claims: 7

1. In a heat-control system of the type wherein a thermostat controls adamper-controlling only comes into play when necessary, and after 1different construction of the end of the lever arm motor connected to asource of power, the combination of means responsive to-a failure of thethe thermostat,for re-setting said power-failure the Oh contacts of saidresponsive means to its position before power failure movement of saidguide by saidraised damper.-

3. The .combination according to claim2, in

Y which said last means includes a solenoid directly connected to thesource of power.

4. The combination according to claim 2, in combination with a pivotallymounted lever arm, and means for mounting said guide on said leverassure tation by said motor, a furnace damper, a chain interconnectingsaid crank-arm with said damper arm, and in which said last means actsupon said guide by restraining movement ofsaid lever arm. 5. Thecombination according to claim 2, in combination with a switch device,means for actuating said switch device upon movement of said guide fromits restrained position, and conductors connecting said switch to saidmotor and source of power to insure movement of said motor to thedamper-lowering position upon restoration of said source of power toremove the effect of the weight of said damper on said guide, and meansfor returning said guide to its restrained position. 6. In a safetydamper-control system of the class including a source of power, a motor,a damper, means including a chain for raising and lowering said damperby said motor, a commutating device driven by said motor, a single-polethermo-responsive switch having on" and "ofi contacts, and conductorsinterconnecting said motor, commutating device and switch to said sourceof power for rotating said motor to raise said damper when said switchis in its "on position and to lower said damper when the switch is inits "ofP position, the combination with a releasable guide for saidchain subjected to the weight of said damper when in its raisedposition, and means responsive to the source of power for restrainingmovement of said guide, but releasing said guide upon power failure topermit closing of said damper.

. 'l. The combination according. to claim 6, in

yfor raising and lowering the latter, a source of power, switching meansfor connecting said motor to said source of power for actuating saidmotor to raise or lower said damper, a releasable guide for said chainpositioned intermediate said crank-arm and said damper and urged in achain-slackening direction by the weight of said damper in its raisedposition, and means responsive to the source of power for restrainingmovement of said guide, whereby upon a power failure when the damper isin its raised position said guide will be released to slacken said chainand lower said damper.

11. The combination according to claim 10, in

combination with means operated upon move-.-

ment of said guide to establish a circuit for said motor in thedamper-lowering direction, whereby upon restoration of power saidcrank-arm will be rotated to remove the efi'ect of the weight of saiddamper on said guide, and means for returning said guide to itsrestrained position.

12. In a releasable safety device, in combination, a pivotally mountedlever arm, a second lever arm pivotally mounted in juxtaposition to saidfirst lever arm, said second lever arm having a stop member adapted toprevent the rotation of said first. lever arm in one direction, springmeans urging said second lever arm for rotation in a direction to removesaid stop from the path of said first lever arm, a solenoid for normallyholding said second lever arm in its stop-en-' gaging position, andmeans for urging said first lever arm toward said second lever arm,whereby said first lever arm acts upon the second lever arm to returnsaid second arm to its normally holding and stop-engaging position.

13. In a damper controlling system, a motor, a crank arm adapted to bedriven by said motor, a furnace damper, means interconnecting said crankarm with said damper for alternately opening and closing the latter uponrotation of said motor and crank arm in one direction, a sourcecombination with a second switch adapted to be closed upon release ofsaid guide, and condu'ctors for connecting said second switch in shuntwith thermo-responsive switch.

8. me combination according to claim 6, in combinationwith means forreturning said guide to its restrained position upon the-restoration ofpower. Y

9. In a damper-control system. in combination, a source of power,-adamper movable between open. and closed positions, an electrical deviceconnected to said source of power,- mechanical means interconnectingsaid electrical device with said damper for opening and closing thesame, and means acting upon said mechanical means for causing closure ofsaid damper in response to failure of said source of power, said lastmeans including a releasable guide, and said mechanical means includinga chain adapted to move said guide in the open position of said damper.

10. In a damper controlling system, in combination, a motor, a crank-armconnected for roof power, switching means for connecting said motor tosaid source of power for actuating said motor to open or close saiddamper, and means operable upon said interconnecting means andresponsive to a failure of the power source for causing closure of thedamper if open in response to the position of said switching means,independently of the position of said crank arm.

14. In a safety damper-control system of the class including a source ofpower. a motor, a damper, means for opening and closing said damper bysaid motor, a commutating device sponsive switch having "on" and "01!contacts,

- and conductors interconnecting said motor, commutating device andswitch to said source of power for rotating said motor to open saiddamper when said switch is in its on" position and to close said damperwhen said switch is in its "01! position, the combination with meansresponsive to a failure of the source of power for causing a closure ofthe damper if open in response to the call ofthe thermo-responsiveswitch and simultaneously establishing a shunt circuit about the 0113"contact of said switch. 1

15. In a releasable safety device, in combination, a pivotally mountedlever arm, a pawl on the end of said lever arm, stop means forpreventing movement of said pawl in one direction, spring means forurging said pawl toward said stop means, a second lever arm pivotallymounted in juxtaposition to said first lever arm, said second and meansfor urging said first lever'arm toward lever arm having an extensionadapted to engage said second lever arm, whereby said first lever saidpawl and move it. toward said stop means arm acts upon thesecond leverarm to return to prevent rotation of said first lever arm in one saidsecond lever arm to its normally holding and direction, a solenoid fornormally holding said 5 pawl-engaging position.

second lever arm in its pawl-engaging position, JOHN T. CARL-SON.

